3 



Am U I'lADACEAE. 



Vol. III. 



1 6. Asclepias syriaca L. Common Milk- 

 weed. Silkweed. Fig. 3398. 



. f.i< lepias 1 in (Oi a I . Sp, PI. . 14. 175.;. 



Asclepias Cornuti Dec. in DC. 1'rodr. 8: 564. 1844. 



Stem stout, usually simple, 3-S high, finely 

 pubescent at lea-: above. Leaves oblong, oval or 

 ovate, finely and densely pubescent beneath, soon 

 glabrous above, acute or obtuse and cuspidate at 

 the apex, obtuse, narrowed .or subcordate at 

 the base, 4.'-g' long, 2'-4i' wide, the primary nerve- 

 wide-spreading; petioles stout, 3"-8" long; umbels 

 several or numerous ; peduncles pubescent or tomen- 

 tose, 1*' 3*' long; pedicels i'-2' long; corolla green- 

 purple or greenish-white, its segments oblong-lan- 

 ceolate, 3"-4" long; column short and thick, the 

 hoods ovate-lanceolate with a tooth on each side, 

 longer than the anthers and the incurved horn ; fol- 

 licles 3'-s' long, erect on recurved pedicels, tomen- 

 tose and covered with short soft processes. 



In fields and waste" places, New Brunswick to Sas- 

 katchewan, North Carolina and Kansas. Leaves rarely 

 lanceolate. Silky swallow-wort. Virginia silk. Wild 

 cotton. June-Aug. 



Asclepias kansana Vail, of Kansas, differs by erect-spreading hoods of the corolla and more 

 densely tomentose follicles. 



17. Asclepias speciosa Torr. Showy Milk- 

 weed. Fig. 3399. 



Asclepias speciosa Torr. Ann. Lye. N. Y. 2 : 218. 1826. 

 A. Douglasii Hook. Fl. Eor. Am. 2: 53. pi. 152. 1834. 



YVhite-tomentose or canescent all over, or gla- 

 brate below, pale; stem simple, stout, i-2 high. 

 Leaves thick, broadly ovate or oval, obtuse and cus- 

 pidate or acute at the apex, subcordate, rounded or 

 narrow-ed at the base, petioled, 3'-8' long, 2'-^ wide ; 

 peduncles 1' 3' long; umbels several or rarely soli- 

 tary, many-flowered; pedicels stout, 0/-18" long; 

 corolla purple-green, its segments oblong or ovate- 

 oblong, 4 - '-6" long, tomentose on the outer face ; 

 column very short or none ; hoods lanceolate, 5"-"" 

 long, obtusish, expanded and with 2 blunt teeth be- 

 low, the apex ligulate, 5-7 times as long as the 

 anthers ; horn short, inrlexed ; follicles erect or 

 spreading on the recurved fruiting pedicels, 3'-4 # 

 long, densely woolly and covered with soft spinose 

 processes. 



In moist soil, Minnesota to British Columbia, south 

 to Kansas. Utah and California. May-July. 



18. Asclepias arenaria Torr. Sand Milk- 

 weed. Fig. 3400. 



A. arenaria Torr. Bot. Mex. Bound. Surv. 16 



1859. 

 stems 



high, 

 thick, 



Densely tomentose-canescent all over, 

 simple, ascending or erect, stout, i-2 

 Leaves obovate or oval, wavy-margined, 

 obtuse or retuse and cuspidate at the apex, trun- 

 cate, subcordate, obtuse, or rarely some of them 

 narrowed at the base, 2'~4' long, 1J-3' wide, the 

 angle of the primary nervation broad ; umbels 

 densely many-flowered, short-peduncled or ses- 

 sile ; corolla greenish-white, its segments oval- 

 oblong, 4"-5" long; column l"-2" high; hoods 

 oblong, truncate at each end, oblique at the apex, 

 longer than the anthers, with a broad tooth on 

 each side within ; horn semi-lunate with an ab- 

 ruptly incurved subulate apex; follicles puberu- 

 lent. 4'-5' long, erect on the decurved fruiting 

 pedicels. 



On sand-bars and hills along rivers, Nebraska and 

 Colorado to Mexico and New Mexico. June-Sept. 



